Migrate OS + data from onboard SCSI to RAID controller

I would like to migrate an excisting OS + data.The disks are now connected to the onboard SCSI port of a Proliant ML370 G3 server and i want them connected on an optional RAID controller without dataloss. I have tried it on a testserver, buth when i connect the disk on the RAID, i have no logical drive. If i made a logical drive, then the data is lost.Does anyone has an idea how to migrate without dataloss.